heckmann



UNITED STATES PATENT OFFICE.

NAPOLEON J. HEGKMANN,

OF LOUGHTON, ENGLAND.

SPECIFICATION forming part of Letters Patent No. 225,282, dated March 9, 18 80. Application filed October 8, 1879. Patented in England, February 6, 1879.

To all whom it may concern Be it known that I, NAPOLEON J OSEPH HEOKMANN, of Loughton, in the county of Essex, England, have invented a new and useful Process for Treating Paper for Detective Purposes, which is fully set forth and described in the following specification.

The improvements are performed by placing in the size (used in the finishing process of pa per-makin g) equal parts of prussiate of potash and sulphuret of ammonia, in the proportions,

or near thereto, of one of each to about twenty of size. The paper or parchment is passed through this solution and finished as in making ordinary paper. Any color or tint can be added, as at present. I prefer, however, to use sulphate of manganese and sulphate of copper, seven of the first to I fonrot'the latter, for the colorin g-matter, added to tWo hundred and forty weight of liquid, consisting of three parts water to one part size, or

snfficient size to cause the paper to float, combined with the detective ingredients first above mentioned.

As most attempts at erasure by chemical means would leave a dark discoloration on paper so treated, great care is necessary in keeping utensils wherein to dissolve the chemicals, as in no case must the ingredients for the coloring come in contact with those chemicals in the first solution, because in that event it would cause a precipitate which would be on the surface of the paper. and not become embodied therein. It is also imperative that the rolls of the sizing-machine be without eruption or indentation, as the re sult would be a streak upon the surface of the paper when passing through the coloring so. lution. This precaution is not necessary when the paper is passing through the first solution. Therefore, to obviate this discoloration, the rolls of the sizer must be coated with at least a half inch in thickness of vulcanized indiarubber.

If ordinary metal rolls be used for the first operation, they should be free of any eruption ofindents on the surface, so as to render them fit for the second or coloring operation. Care must be taken that after the paper has passed through the first solution the rolls and the size-trough be thoroughly cleansed with a solution consisting of one part sulphuric acid to eight parts of water, until the discoloration caused by the sulphuret of ammonia is removed. Should the rolls be covered with vulcanized rubber it will only be necessary to use clean water to remove any traces of thefirst solution before using the second. It is further necessary that the sizing -trough be at least twelve inches away from the back of the rolls, because, if such be not the case, the froth caused by the paper passing through the second solution would attach itself to the paper in the shape of small globules, and so prevent the second solution from attaching itself to the already sensitized paper, and there by causing White spots.

The best paper for use is that known by the term water-leaf.

The first solution is best formed of half size and half water of not less temperature than that ordinarily used for sizing paper. the chemicals, previously dissolved separately, to be added separately. l

The second solution is best formed of three parts water to one part size, or sufficient size to cause the paper to float on the rolls.

In the drying process the temperature in the drying-room must not exceed 80 or 90 Fahrenheit, for if in excess it renders the paper harsh.

I claim as my invention- The process of preparing detective-paper by placing in the finishing-size prussiate of potash and sulphuret of ammonia, substantially in the manner described.

In testimony whereof I have signed this specification in the presence of two subscribing witnesses.

N. J. HEGKMANN. 

